In fact we went to a safe altitude and he showed me exactly what happens when you go from full to 0 flap and just how much altitude you can lose.
If you are talking about retracting the flap from full down to up in one go in a Cessna 152, you shouldn't normally lose more than 100 feet of altitude providing you adjust the nose attitude up to cover the slight sink. Your instructor sounds like a panic merchant if he shouted loudly and snatched the flap lever out of your hand then climbed to a "safe" altitude. What did your instructor consider a "safe" altitude? Sounds like the instructor needs retraining.
It is only a Cessna 152 for goodness sake. Check the C152 Cessna Information manual where it states: In a baulked landing (go-around) climb the wing flap setting should be reduced to 20 degrees immediately after full power is supplied. Upon reaching a safe airspeed 55 knots wing flaps retract slowly.